Petrel Checkshot Data Import

Importing checkshots making sure the depth and time indexes get correct (+/-) signs

Conventions for checkshot import  MD, TVD or Z can be used as depth index.

•

 MD refers to KB, and Z to MSL. TVD can be set to refer to KB, MSL, SRD (Seismic Reference Datum) or CRD (Checkshot Reference Datum). TWT can be set to refer to SRD or CRD •

 In Petrel, by convention Z and TWT have NEGATIVE values in the underground, and MD and TVD have POSITIVE values in the underground •

 The table below represent the uppermost part of the checkshot applied to the well to the right (KB=36m) •

MD (m)

TVDSS (m)

Z (m)

TWT (ms)

36.00

0.00

0.00

0.00

121.91

85.94

-85.94

-110.30

243.82

207.86

-207.86

-258.20

365.74

329.77

-329.77

-397.90

487.66

451.68

-451.68

-530.80

Note that when the Domain of the window is TWT the Z-axis refers to TWT values

Domain: TWT

Import checkshots dialog  In this example the checkshots file to be imported have positive Z and TWT values. The options ”Negate Z values” and ”Negate time values” must be toggled on to make Petrel read the Z and TWT values as they were negative. •

By default the ”Negate Z values” and ”Negate time values” are toggled on in the Import checkshots dialog. •

 Note that checkshots exported from Petrel will have negative Z and TWT values. Consequently importing checkshots exported from Petrel using default settings in the Import dialog will give be incorrect. •

 QC the imported checkshots by displaying the well in a 3D window in TWT domain, and open the Checkshot spreadsheet to confirm that the Depth and Time indexes have correct signs. •

Note that the in Checkshot spreadsheet the TWT values are denoted with positive values in the underground